System and method to define a rotational source associated with a biological rhythm disorder

ABSTRACT

An example system and method of defining a rotational source associated with a heart rhythm disorder are disclosed. A plurality of center locations of wave fronts are calculated at a plurality of time points associated with the heart rhythm disorder. A rotational path that connects the plurality of center locations is then determined. Thereafter, a clinical representation that identifies a region of heart tissue associated with the rotational path is generated. The system and method can also determine a likely core associated with the rotational path. A plurality of relative diffusion shapes associated with the plurality of the center locations is calculated. A plurality of intersecting points of a smallest relative diffusion shape and other relative diffusion shapes is determined within the rotational path. A bounded polygon of the intersecting points is defined as the likely core.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/220,662, filed on Mar. 20, 2014, now U.S. Pat. No. 9,398,860, whichis a continuation of U.S. patent application Ser. No. 13/840,354, filedon Mar. 15, 2013, now U.S. Pat. No. 8,715,199, the contents of which areincorporated herein by reference in their entirety.

BACKGROUND

1. Field

The present application relates generally to biological rhythmdisorders. More specifically, the present application is directed to asystem and method to define a rotational source associated with abiological rhythm disorder, such as a heart rhythm disorder.

2. Brief Discussion of Related Art

Heart (cardiac) rhythm disorders are common and represent significantcauses of morbidity and death throughout the world. Malfunction of theelectrical system in the heart represents a proximate cause of heartrhythm disorders. Heart rhythm disorders exist in many forms, of whichthe most complex and difficult to treat are atrial fibrillation (AF),ventricular tachycardia (VT) and ventricular fibrillation (VF). Otherrhythm disorders are more simple to treat, but may also be clinicallysignificant including atrial tachycardia (AT), supraventriculartachycardia (SVT), atrial flutter (AFL), supraventricular ectopiccomplexes/beats (SVE) and premature ventricular complexes/beats (PVC).

Previously, treatment of heart rhythm disorders—particularly complexrhythm disorders of AF, VF and polymorphic VT—has been difficult becausethe location in the heart that harbors the source of the heart rhythmdisorder could not be identified. There have been various theories ofhow complex rhythm disorders function and clinical applications fortreating these complex rhythm disorders. However, none of theapplications proved fruitful in the treatment of complex rhythmdisorders.

Recently, there has been a breakthrough discovery that for the firsttime identified sources associated with complex heart rhythm disorders.This technological breakthrough successfully reconstructed cardiacactivation information (onset times) in signals obtained from electrodesof catheters introduced into patients' heart to identify rotationalactivation patterns (rotational sources) that cause a large percentageof the heart rhythm disorders worldwide. Treatment of the heart rhythmdisorders can thus be targeted to the rotational sources in thepatients' heart to eliminate the heart rhythm disorders. Such treatmentcan be successfully delivered by ablation, for example.

While a rotational source of a complex heart rhythm disorder can beidentified as described above, the extent or breadth of the propagationof the rotational source and its likely center of rotation have not beendefined. In some instances, a rotational source may have one or morediffuse sections (activation wave fronts) that generally appear torotate around a subjective rotation center, but tend to spread outdiffusely about a section of the patient's heart. While the diffuseactivation wave fronts are associated with the source of the complexrhythm disorder, they may contribute insignificantly to driving theheart rhythm disorder than one or more other activation wave fronts ofthe rotational source.

There are no known systems or methods to define a rotational sourceassociated with a heart rhythm disorder, including a rotational path anda likely center of rotation associated with the rotational source.

SUMMARY

The present disclosure is applicable to various rhythm disorders,including heart rhythm disorders, as well as other biological rhythmdisorders, such as neurological seizures, esophageal spasms, bladderinstability, irritable bowel syndrome, and other biological disordersfor which biological activation information has to be reconstructed topermit determination, diagnosis, and/or treatment of a rotational sourcecausing the biological rhythm disorders. It is particularly useful,however, in complex rhythm disorders of the heart, in order to find thecore of the rotational sources of the disorders such that they can betreated with precision and expediency.

Among the advantages of the present disclosure is the ability to usereconstructed cardiac (or biological) activation information associatedwith a rotational source of the rhythm disorder such that adetermination of a core of the rotational source can be determined andtreated.

Another advantage is that the present invention provides a system and amethod, which can be carried out rapidly while a sensing device—such asa catheter having sensors thereon—is used in or near the patient and canbe followed by treatment of cardiac tissue to ameliorate the rhythmdisorder and in many cases cure the rhythm disorder. Treatment may thusoccur immediately upon computing the core of the source of the rhythmdisorder, since it will provide the location in the patient of the corethat is driving the rotational source.

Still another advantage of the present disclosure is that preciseidentification of the core for the rotational source can help eliminatethe heart rhythm disorder, while also helping to limit or spare thedestruction of otherwise healthy heart tissue of the patient that mayonly insignificantly contribute to driving the source of the heartrhythm disorder.

As used herein, reconstructed activation information is signal data ofcardiac or biological signals each of which has been processed toidentify activation onset times at a sensor location distinct fromnearby or adjacent sensor locations for one or more beats of abiological or cardiac rhythm disorder.

As used herein, activation onset time is a time point at whichactivation commences in a cell or tissue of a patient, as opposed toother time points during activation.

As used herein, activation is a process whereby a cell commences itsoperation from a quiescent (diastolic) state to an active (electrical)state.

In accordance with an embodiment or aspect, a method of defining arotational source associated with a heart rhythm disorder is disclosed.A plurality of center locations of wave fronts are calculated at aplurality of time points associated with the heart rhythm disorder. Arotational path that connects the plurality of center locations is thendetermined. Thereafter, a clinical representation that identifies aregion of heart tissue associated with the rotational path is generated.

The method can also include determination of a likely core associatedwith the rotational path. A plurality of relative diffusion shapesassociated with the plurality of the center locations is calculated. Aplurality of intersecting points of a smallest relative diffusion shapeand other relative diffusion shapes is determined within the rotationalpath. A bounded polygon of the intersecting points is defined as thelikely core.

In accordance with an embodiment or aspect, a system to define arotational source associated with a heart rhythm disorder is disclosed.The system includes a computing device and a machine-readable medium tostore instructions that, when executed by the computing device, causethe computing device to perform certain operations. The operationsinclude calculating a plurality of center locations of wave fronts at aplurality of time points associated with the rotational source. Theoperations also include determining a rotational path that connects theplurality of center locations. The operations further include generatinga clinical representation that identifies a region of heart tissueassociated with the rotational path.

The computing device can also perform operations for determining alikely core associated with the rotational path. These operationsinclude calculating a plurality of relative diffusion shapes associatedwith the plurality of the center locations. These operations alsoinclude determining a plurality of intersecting points of a smallestrelative diffusion shape and other relative diffusion shapes within therotational path. These operations further include defining a boundedpolygon of the intersecting points as the likely core.

In accordance with still another embodiment or aspect, a tangiblecomputer-readable medium that stores instructions which, when executedby a processor, cause the processor to perform operations for defining arotational source associated with a heart rhythm disorder, is disclosed.The operations include calculating a plurality of center locations ofwave fronts at a plurality of time points associated with the rotationalsource. The operations also include determining a rotational path thatconnects the plurality of center locations. The operations furtherinclude generating a clinical representation that identifies a region ofheart tissue associated with the rotational path

The tangible computer-readable medium can also store instructions which,when executed by a processor, cause the processor to perform operationsfor determining a likely core associated with the rotational path. Theseoperations include calculating a plurality of relative diffusion shapesassociated with the plurality of the center locations. These operationsalso include determining a plurality of intersecting points of asmallest relative diffusion shape and other relative diffusion shapeswithin the rotational path. These operations further include defining abounded polygon of the intersecting points as the likely core.

The above-described embodiments or aspects can further accessreconstructed signal data having activation onset times associated withvoltages at the plurality of time points. The signal data can betransformed from spline-sensor references to locations having associatedcoordinates.

The above-described embodiments or aspects can further determine thewave fronts to include adjacent locations having at least a thresholdvoltage level surrounded by locations below the threshold voltage level.The threshold voltage level can be a predetermined percentage of ahighest voltage.

The above-described embodiments or aspects can further determine aconvex hull around the rotational path, such that the plurality ofintersecting points of the smallest relative diffusion shape and otherrelative diffusion shapes can be determined to be inside the convex hullin order to define the likely core.

The above-described embodiments or aspects can further include adetermination of a center location of a wave front. All firstcoordinates of locations associated with the wave front are averaged togenerate a first average coordinate. All second coordinates of thelocations associated with the wave front are averaged to generate asecond average coordinate. Thereafter, center location of the wave frontis defined as a location identified by the first average coordinate andthe second average coordinate.

The above-described embodiments or aspects can further calculate arelative diffusion shape of a wave front. The calculation can includedetermining distances from locations in the wave front to a centerlocation of the wave front, and calculating a circle having a radiusequal to a predetermined multiplier multiplied by a standard deviationof the distances. The predetermined multiplier can be equal to two.

These and other purposes, goals and advantages of the presentapplication will become apparent from the following detailed descriptionread in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments or aspects are illustrated by way of example and notlimitation in the figures of the accompanying drawings in which:

FIG. 1 illustrates an example graphical mapping of an example rotationalsource associated with a heart rhythm disorder in a patient;

FIG. 2 illustrates an example x-y coordinate graphical mapping of aspline-sensor element in FIG. 1;

FIG. 3 illustrates a first example activation wave front of a rotationalsource illustrated in FIG. 1 at a first example time point, astransformed into a first wave front (island) with a threshold applied toassociated voltages;

FIG. 4 illustrates a second example activation wave front of arotational source illustrated in FIG. 1 at a second example time point,as transformed into a second wave front (island) with a thresholdapplied to associated voltages;

FIG. 5 illustrates the averaging of x-y coordinate locations thatcontribute to an example island represented by the x-y coordinategraphical mapping in FIG. 2;

FIG. 6 illustrates an average center location based on calculated centerlocations of the constituent islands in FIGS. 3, 4 inside a vector path;

FIG. 7 illustrates relative spatial diffusions of the islands inrelation to the vector path which have center locations that form thevector path;

FIG. 8 illustrates an example method of calculating a relative spatialdiffusion of an island in relation to the vector path;

FIG. 9 illustrates relative diffusions of islands in FIG. 7 relative totheir center locations at respective time points in relation to thevector path;

FIG. 10 illustrates determination of an example core associated with arotational source of a heart rhythm disorder illustrated in FIG. 1;

FIG. 11 is a flowchart that illustrates an example method of determininga rotational path and identifying a likely core associated with arotational source of a biological rhythm disorder, such as a rotationalsource of the heart rhythm disorder illustrated in FIG. 1; and

FIG. 12 is a block diagram of an illustrative embodiment of a generalcomputing system.

DETAILED DESCRIPTION

A system and method to define a rotational source of a biological rhythmdisorder, such as a heart rhythm disorder, is disclosed herein. In thefollowing description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of example embodiments or aspects. It will be evident,however, to one skilled in the art, that an example embodiment may bepracticed without all of the disclosed specific details.

FIG. 1 illustrates an example graphical mapping 100 of an examplerotational source 106 associated with a heart rhythm disorder in apatient. For example, the rotational source 106 is a source of a heartrhythm disorder in a right atrium of the patient's heart that isobserved to progress in a counter-clockwise rotational pattern about asubjective rotation center 112 (one or more of the locations marked withquestion marks), which can be evaluated by a physician to be along theelectrode reference 104, anywhere between about electrodes 4-5-6, andalong the spline reference 102, anywhere between about splines B-C, of abasket-type catheter (not shown) introduced into the patient's heart. Itis noted that the rotational sources of different heart rhythm disorderscan be disposed at different locations in different chambers of theheart and can rotate in different directions (e.g., clockwise) aboutvarious centers of rotation.

The example rotational source 106 can include a plurality of activationmappings 108, 110 that progress in the counter-clockwise rotationalpattern about the subjective rotational center 112 over time of a cycle,e.g., 100 ms-300 ms. Each of the activation mappings 108, 110 caninclude elements 114 that represent a charge level (or voltage level) ofa sensor at a spline reference 102 and a sensor reference 104. Theactivation mappings 108, 110 represent reconstructed activationinformation (reconstructed signal data of cardiac signals) identifyingactivation onset times at a plurality of sensors for one or more beatsof a cardiac rhythm disorder. For example, the activation mappings 108,110 can be generated by the system and method for reconstructing cardiacactivation information patented in U.S. Pat. No. 8,165,666, which isincorporated herein by reference in its entirety.

For example, the activation mappings 108, 110 (or activation wavefronts) can be a monophasic action potential (MAP) voltagerepresentation generated for multiple processed cardiac signals shown inFIG. 11 of the '666 patent. Specifically, multiple cardiac signals areprocessed as described in the '666 patent and MAP representations aregenerated based on these processed signals. The electrical activity ofall the MAP representations can be mapped in a sequence showing theexample activation mappings 108, 110 at different time points, e.g.,activation mapping 108 being earlier than activation mapping 110. Whileonly two activation mappings 108, 110 (or activation wave fronts) areshown for clarity and brevity of this disclosure, it should be notedthat additional activation mappings can be part of the rotational source106 about the subjective rotation center 112.

Similarly, other systems and methods that can reconstruct cardiac orbiological activation information to generate rotational sources can beused as input into the present system and method of determining arotational path and identifying a likely core of rotation associatedwith these rotational sources.

In some instances, a rotational source 106 may have one or more diffusesections, such as activation wave front 108. The activation wave front108 generally rotates around the subjective rotation center 112,spreading out diffusely about a section of the patient's heart, andappears to contribute insignificantly to driving the heart rhythmdisorder than one or more other activation wave fronts 110 of therotational source 106. Accordingly, FIGS. 2-11 described below ingreater detail will elucidate how to computationally determine arotational path and identify a likely core of the rotational source 106more precisely than the subjective rotation center 112, as describedhereinabove with reference to FIG. 1.

FIG. 2 illustrates an example Cartesian (x-y coordinate) graphicalmapping 200. The Cartesian graphical mapping 200 presents an examplemethod of transforming reconstructed signal data of cardiac signals fromthe spline/electrode references 102, 104 illustrated in the graphicalmapping 100 to the x-y coordinates illustrated in this Cartesiangraphical mapping 200, which are used in one or more calculations and/ordeterminations described with reference to FIGS. 3-11.

For example, the Cartesian graphical mapping 200 extends from x-y (0, 0)to x-y (28, 28). The example plurality of x-y coordinate locations 202can represent the element 114 of activation wave front 110 in FIG. 1.The coordinate locations 202 (including locations 204-212) and theirassociated charge (voltage) levels can be interpolated from the element114 of the graphical mapping 100. Accordingly, the other elements of theactivation wave fronts 108, 110 in FIG. 1 can be similarly transformedto the Cartesian coordinates.

A transformation Tx 214 can transform an x-y coordinate location to aspline-electrode reference. For example, a location at an x-y coordinate(4, 8) can be transformed to the following spline-electrode reference:spline=((x+1)/4)+A=((4+1)/4)+A=1.25+A=B; andelectrode=((y+1)/4)+1=((8+1)/4)+1=2.25+1=3.25=3.

In some embodiments, the spline-electrode reference values are roundedto a nearest whole spline and whole electrode. In various otherembodiments, a fractional spline can be utilized for certainapplications.

A transformation Rx 216 is a reverse of the transformation Tx 214. Thetransformation Rx 216 can transform the foregoing spline-electrodereference to an x-y coordinate location. For example, thespline-electrode location B-3 can be transformed to the following x-ycoordinate location:x=4(spline-A)=4(B-A)=4(1)=4; andy=4(electrode-1)=4(3-1)=4(2)=8.

In the foregoing examples, the electrodes have the benefit of actualnumbers assigned to them. However, the splines have letters assigned. Toperform mathematical operations set forth above, the splines arerepresented by numbers as follows: A, B . . . H represented by 1, 2 . .. 8. Accordingly, the following spline calculations can be easilyperformed:

A − A = (1 − 1) = 0; B − A = (2 − 1) = 1; … H − A = (8 − 1) = 7.

The spline representations can also be used to perform other splinecalculations, such as addition, as well as other mathematicalcalculations.

FIG. 3 illustrates the sample activation wave front 108 of therotational source 106 illustrated in FIG. 1 at an example time point T₀,as transformed into a Cartesian wave front (island) 300 with thresholdapplied to the associated charges (voltages). While the island 300 lookssimilar to the activation wave front 108, it should be noted that onlythose Cartesian coordinate locations are represented that are adjacentlylocated and are above a charge (voltage) threshold, as described ingreater detail below.

More specifically, a threshold of top 18% is applied to the charges(voltages) of elements in the activation wave front 108. Accordingly,when spline-electrode references of the activation wave front 108 aretransformed into associated locations of the Cartesian wave front(island) 300, the only locations that are identified and marked forinclusion in the island 300 and used in later calculations, as describedherein, are those adjacent locations that are above the threshold charge(voltage). The locations are marked with the threshold charge (voltage)level. More specifically, the adjacent locations that are above thethreshold define the island of locations which are above the thresholdwith other locations surrounding the island which are below thethreshold.

Moreover, five charge (voltage) levels 324-332 can be defined in thethreshold, with each level being 3.6% of the threshold (e.g., top 18% ofcharges for the island). Specifically, the highest charge level 324 isdefined as [0%-3.6%] of the top 18% of charges (voltages) in theactivation wave front 108. Charge levels 326, 328, 330 and 332 aredefined, respectively, as [3.6%-7.2%], [7.2%-10.8%], [10.8%-14.4%], and[14.4%-18.0%]. While a threshold of 18% is used, other thresholds can bedefined.

As further illustrated in FIG. 3, eleven (11) time points T₀-T_(N) areassociated with the rotational source 106 as it completes a cycle ofactivation. Each of the time points can be about 10 ms to about 30 msapart, for a total time of about 100 ms to about 300 ms, as describedherein in association with a cycle of a heart rhythm disorder. A largernumber of time points can be used in association with a cycle of a heartrhythm disorder. For example, each time point can be about 1 ms apart,or another higher time interval apart.

The x-y coordinate locations that contribute to the island 300 areaveraged to compute a center location 302 at the example time point T₀.The calculation of the center location at a time point will beillustrated in greater detail with reference to FIG. 5 below. Similarly,center locations 304, 306 . . . 322 are calculated for the islands atthe time points T₁-T_(N).

The center locations 302, 304 . . . 322 in the islands 300 and others(all islands not shown) at the time points T₀-T_(N) over a course of afull cycle define a vector path 301 that is associated with a likelycore of the rotational source 106 illustrated in FIG. 1. As illustratedin FIG. 3, the vector path 301 includes vectors 303, 305 . . . 323extending between and contacting the center locations 302, 304 . . .322.

FIG. 4 illustrates the sample activation wave front 110 of therotational source 106 illustrated in FIG. 1 at an example time point T₄,as transformed into Cartesian wave front (island) 400 with a thresholdapplied to the associated charges (voltages). Similar computations areperformed to define the island 300, as described hereinabove withreference to island 400 in FIG. 3.

Specifically, the x-y coordinate locations that contribute to the island400 are averaged to compute a center location 310 at the example timepoint T₄. As previously described, the center locations 302, 304 . . .322 in the islands 300, 400 and others (all islands not shown) at thetime points T₀-T_(N) over a course of the full cycle define the vectorpath 300 that is associated with a likely core of the vector path 301,e.g., a likely core of the rotational source 106 illustrated in FIG. 1.

FIG. 5 illustrates the averaging of x-y coordinate locations thatcontribute to an example island, represented by the graphical mapping200 illustrated in FIG. 2.

As particularly illustrated in FIG. 5, the x-coordinates of thelocations 204-212 in the island 200 (as set forth in FIG. 2) areaveraged to determine a mean x-coordinate of 5.2. Similarly, they-coordinates of the locations 204-212 in the island 200 (as set forthin FIG. 2) are averaged to determine a mean y-coordinate of 8.6. Itshould be noted that the x-y coordinates of the locations 204-212represent their centers.

Accordingly, the calculated averages of the x-coordinates and they-coordinates of locations in the island 200 define a center location502 for the island as an x-y coordinate location (5.2, 8.6).

FIG. 6 illustrates an average center location 602 based on thecalculated center locations 302, 304 . . . 322 of the constituentislands 300, 400 in FIGS. 3, 4 and others islands (not shown) inside thevector path 301.

As illustrated in FIG. 6, the average center location 602 based on thecenter locations 302, 304 . . . 322 at the time points T₀-T_(N)identifies an x-y coordinate location inside the vector path 301, whichis transformed into a spline-electrode reference (using FIG. 2) to beapproximately between splines C-D and electrode 5, as marked by alocation identified by a triangle R_(AVG).

It is clear that a number of diffuse islands, such as the island 300 ofFIG. 3, tend to bias the computed average of the center locations of allthe islands towards an approximate center location (R_(AVG)) of thevector path 301, rather than a location about the subjective rotationcenter 112 that was expected to be between about splines B-C (andelectrodes 4-5-6), as described hereinabove with reference to in FIG. 1.The description hereinbelow with FIGS. 7-10 illustrates a method toeliminate the biasing produced by the diffused islands, such as island300.

FIG. 7 illustrates relative spatial diffusions 702, 704 of the islands300, 400 in relation to the vector path 301 illustrated in FIGS. 3, 4,as well as others islands (not shown) which have center locations thatform the vector path 301.

It has been determined that the islands (wave fronts) of the source ofthe rhythm disorder that are relatively spatially distributed (diffused)over a relatively wide portion of the heart (e.g., island 300) inrelation to the vector path 301 can include locations that areinfluenced not only by a likely core of the source of the heart rhythmdisorder, but also by other portions of the heart that are potentiallyunrelated to an electrical pathway associated with the likely core ofthe source of the heart rhythm disorder.

It has further been determined that those locations of the islands (wavefronts), which are focused in a relatively smallest spatial distribution(e.g., island 400) in relation to the vector path 301, represent afocused link of continuity associated with an electrical circuit drivenby the likely core of the source of the heart rhythm disorder andtherefore are associated with the electrical pathway needed to sustainthe source of the heart rhythm disorder.

An example method of calculating relative spatial diffusion in relationto the vector path 301 is described below in relation to FIG. 8. Othermethods of determining the relative diffusion can be utilized.

FIG. 8 illustrates an example method 800 of calculating a relativespatial diffusion of an island in relation to a vector path. In thisexample, the mapping 200 of FIG. 2 is considered to be an island (wavefront) whose center location 502 at the coordinate location (5.2, 8.6)lies along a vector path.

As illustrated in FIG. 5, the x-coordinates of the locations 204-212 inthe island 200 (as set forth in FIG. 2) are averaged to determine a meanx-coordinate of 5.2. Similarly, the y-coordinates of the locations204-212 in the island 200 (as set forth in FIG. 2) are averaged todetermine a mean y-coordinate of 8.6. Accordingly, the calculated centerlocation 502 for the island 200 is the x-y coordinate pair (5.2, 8.6).

A distance d 802 is determined for each of the locations 204-212. Thedistance d 802 represents a distance from the x-y coordinate of eachlocation to the calculated center location 502 of the island 200. Forexample, an equation 808 illustrates a distance calculation 804 whichcalculates the distance d 802 from the location 208 (4, 9) to the centerlocation 502 (5.2, 8.6) to be d=1.265. Similarly, the distances d arealso calculated for all other constituent locations of the island 200.The distances d for all locations 204-212 of the island 200 are given inthe table 803.

The relative diffusion of the island 200 is represented by a circle 804having a radius 806 from the center location 502 that is equal to thesecond standard deviation of distances from all locations 208-212 to thecenter location 502 of the island 200. For example, the radius 806 isgiven by an equation 810 in which a standard deviation of all distancesis s=0.894 and a second standard deviation is 2s=1.788. Accordingly, therelative diffusion of the island 200 is represented by a circle having aradius of 1.788 from the center location 502 (5.2, 8.6).

The relative diffusions 702, 704 of islands 300, 400 in relation to thevector path 301 illustrated in FIG. 7, as well as others islands (notshown) which have center locations that form or lie along the vectorpath 301, can be calculated using the example method 800 describedhereinabove.

FIG. 9 illustrates relative diffusions 902-922 of islands 300, 400 ofFIG. 7 relative to their center locations 302, 310 at respective timepoints t₀, t₄, and other islands (not shown) in relation to their centerlocations 304-308, 312-322 at respective time points t₁-t₃, t₅-t_(N),all of the foregoing in relation to the vector path 301.

As illustrated, the spatial distributions 902-922 are represented by thecomputed circles 902-922 whose radii represent the relativedistributions or diffuseness of the islands at the time points t₀-t_(N)in relation to the vector path 301. The relevance of each of the circles902-922 to the likely core of the rotational source (e.g., subjectivecenter of rotation 112 illustrated in FIG. 1) is inversely proportionalto the size of each of the circles 902-922 at a respective time pointt₀-t_(N). However, the average location R_(AVG) 602 is skewed toward thelarger circles (with larger radii). Accordingly, it is expected that thelikely core of the rotational source lies at a location that is towardthe smaller circles 910-916.

FIG. 10 illustrates determination of an example likely core 1018associated with a rotational source 106 of a heart rhythm disorderillustrated in FIG. 1.

As particularly illustrated in FIG. 10, the vector path 301 connects thecenter locations 302-322 (illustrated in FIG. 3) for all time pointst₀-t_(N) in relation to the vector path 301. A convex hull 1002 isdetermined for the vector path 301. The convex hull 1002 represents aconvex shape around the vector path 301 constructed from the centerlocations 302-322 at the time points t₀-t_(N).

More specifically, a convex hull is a smallest convex polygon thatsurrounds a set of (x,y) coordinate locations. The convex hull can bethought of as a shape formed by stretching a rubber band around the setof the coordinate locations to define a set of outside perimeter edges.Coordinate locations that are not located on the outside perimeter edgesare, therefore, internal and do not contribute to stretching of theshape.

Computational geometry includes several established algorithms toconstruct a convex hull. An example of such algorithms includes aso-called giftwrap algorithm, which finds shortest flat sides of aconvex shape that surround a set of points. The giftwrap algorithmoperates by folding a hypothetical sheet of wrapping papercounter-clockwise around outside edges of the set of points until onefull revolution around the set of points is completed (e.g., such that alast side touches a first side), resulting in a convex polygon (convexhull).

Accordingly, the convex hull 1002 is determined to smooth the perimeterof the vector path 301 by ignoring internal excursions of the vectorpath 301 that zigzag to the interior of outside perimeter edges, e.g.,vectors 303, 305 . . . 323 associated with the vector path 301. A degreeof difference between the shape of the vector path 301 and the convexhull 1002 around that vector path 301 can indicate a measure of theeccentricity associated with the vector path 301 (e.g., many internalexcursions would indicate a more erratic vector path 301).

A circle having the smallest radius (e.g., smallest circle 912) isselected with its center location 310 (illustrated in FIG. 3) as ananchor. A set of intersecting points 1004-1014 is determined inside theconvex hull 1002—starting with the smallest circle 912 and the adjacentcircles 910, 914, 916, 918 and 920—which define an inscribed polygon1016 inside the convex hull 1002.

Thereafter, the likely core R_(core) 1018 of the rotational source 106associated with the heart rhythm disorder illustrated in FIG. 1 isdefined as a subset of the intersecting points 1004-1014 (e.g.,inscribed polygon 1016), which represents a bounded convex polygoninside the set of intersecting points 1004-1014 (inscribed polygon 1016)and within the convex hull 1002.

FIG. 11 is a flowchart that illustrates an example method 1100 ofdetermining a rotational path and identifying a likely core that areassociated with a rotational source of a biological rhythm disorder,such as a rotational source 106 of the heart rhythm disorder illustratedin FIG. 1. The example method 1100 can be performed by the computingsystem 1200 described hereinbelow in greater detail with reference toFIG. 12.

More specifically, the example method 1100 starts at operation 1102 atwhich reconstructed signal data (e.g., having assigned activation onsettimes) associated with the rotational source 106 of a heart rhythmdisorder in FIG. 1 is provided or can be accessed by the example method1100. At operation 1104, a time point is selected, such as a time pointT₀ of time points T₀-T_(N), as illustrated in FIG. 3.

At operation 1106, the reconstructed signal data is accessed for theselected time point. At operation 1108, the signal data is transformedfrom spline-electrode references to Cartesian coordinate locations thatare associated with voltage levels at the activation onset times.Example transformations are described with reference to FIG. 2.

A threshold level is applied to the coordinate locations at operation1110, with the coordinate locations being marked based on a top level ofcharge (voltage) in the signal data at the selected point of time, e.g.,T₀. As described herein with reference to FIG. 3, the threshold levelrepresenting a top 18% of charges or another threshold level can beapplied to the coordinate locations.

At operation 1112, an island (wave front) including adjacent coordinatelocations at or above the threshold level that is surrounded bycoordinate locations below the threshold level is determined. Exampleisland determinations are described with reference to FIGS. 3 and 4. Atoperation 1114, a center location is calculated for the coordinatelocations in the island. An example calculation of a center location inan island is described with reference to FIG. 5.

A relative diffusion of the island is determined at operation 1116. Therelative diffusion can be a circle having a radius representative of thediffusion of locations in the island. An example calculation of therelative diffusion is described with reference to FIG. 8.

It should be noted that the foregoing data that is accessed,transformed, determined and calculated can be stored (such as incomputer memory or storage device) for later use in accordance with theexample method 1100.

At operation 1118, a determination is made as to whether there are moretime points to process, such as time points T₁-T_(N). If there are moretime points to process as determined at operation 1118, the operations1104-1116 are repeated for the next time point (e.g., time point T₁) andso on until all time points (T₀-T_(N)) have been processed. After adetermination is made that there are no more time points to process atoperation 1118, then the method 1100 continues at operation 1120.

Thereafter, at operation 1120 a vector path that connects the centerlocations at all of the time points (T₀-T_(N)) is determined. An exampledetermination of the vector path is described with reference to FIG. 3.At operation 1122, a convex hull is determined from the vector path. Anexample determination of a convex hull is described with reference toFIG. 10.

A circle having a smallest radius (smallest circle) is selected atoperation 1124. Then, a set of intersecting points (e.g., inscribedpolygon) associated with the smallest circle anchored at its centerlocation and other circles inside the convex hull is determined atoperation 1126. At operation 1128, a determination is made as to whetherformation of a bounded convex polygon is possible inside the set ofintersecting points within the convex hull. If it is determined that thebounded convex polygon can be formed, then the method 1100 continues atoperation 1130. Alternatively, the method continues at operation 1132.

At operation 1130, a likely core of the rotational source 106 of theheart rhythm disorder of FIG. 1 is defined as a subset of theintersecting points that form the bounded convex polygon inside theconvex hull. An example of operations 1124-1130 is also described withreference to FIG. 10. At operation 1132, the method 1100 ends.

In operation, the rotational source 106 of the heart rhythm disorderillustrated in FIG. 1, as defined according to the foregoing disclosure,can be treated in the patient's heart to eliminate the heart rhythmdisorder. For example, heart tissue of the patient on or within thedefined rotational path 301 can thus be targeted for treatment. In caseswhere the likely core 1018 is identified, treatment can be targeted toheart tissue on or within the likely core 1018, sparing heart tissueoutside the likely core 1018. In various cases, a margin beyond therotational path 301 or the likely core 1018 can be established fortreatment purposes. For example, a region of heart tissue slightlylarger (e.g., a millimeter or several millimeters) than the rotationalpath 301 or the likely core 1018 can be targeted for treatment.

The treatment can be successfully delivered to the targeted heart tissue(rotational path 301 or likely core 1018—with/without margin) byablation, for example. Other treatments of the targeted heart tissue areof course possible, e.g., various energy sources (including but notlimited to radiofrequency, cryoenergy, microwave, and ultrasound), genetherapy, stem cell therapy, pacing stimulation, drug or other therapy.

FIG. 12 is a block diagram of an illustrative embodiment of a generalcomputing system 1200. The computing system 1200 can include a set ofinstructions that can be executed to cause the computing system 1200 toperform any one or more of the methods or computer based functionsdisclosed herein. The computing system 1200, or any portion thereof, mayoperate as a standalone device or may be connected, e.g., using anetwork 1224 or other connection, to other computing systems orperipheral devices.

The computing system 1200 may also be implemented as or incorporatedinto various devices, such as a personal computer (PC), a tablet PC, apersonal digital assistant (PDA), a mobile device, a palmtop computer, alaptop computer, a desktop computer, a communications device, a controlsystem, a web appliance, or any other machine capable of executing a setof instructions (sequentially or otherwise) that specify actions to betaken by that machine. Further, while a single computing system 1200 isillustrated, the term “system” shall also be taken to include anycollection of systems or sub-systems that individually or jointlyexecute a set, or multiple sets, of instructions to perform one or morecomputer functions.

As illustrated in FIG. 12, the computing system 1200 may include aprocessor 1202, e.g., a central processing unit (CPU), agraphics-processing unit (GPU), or both. Moreover, the computing system1200 may include a main memory 1204 and a static memory 1206 that cancommunicate with each other via a bus 1226. As shown, the computingsystem 1200 may further include a video display unit 1210, such as aliquid crystal display (LCD), an organic light emitting diode (OLED), aflat panel display, a solid state display, or a cathode ray tube (CRT).Additionally, the computing system 1200 may include an input device1212, such as a keyboard, and a cursor control device 1214, such as amouse. The computing system 1200 can also include a disk drive unit1216, a signal generation device 1222, such as a speaker or remotecontrol, and a network interface device 1208.

In a particular embodiment or aspect, as depicted in FIG. 12, the diskdrive unit 1216 may include a machine-readable or computer-readablemedium 1218 in which one or more sets of instructions 1220, e.g.,software, can be embedded, encoded or stored. Further, the instructions1220 may embody one or more of the methods or logic as described herein.In a particular embodiment or aspect, the instructions 1220 may residecompletely, or at least partially, within the main memory 1204, thestatic memory 1206, and/or within the processor 1202 during execution bythe computing system 1200. The main memory 1204 and the processor 1202also may include computer-readable media.

In an alternative embodiment or aspect, dedicated hardwareimplementations, such as application specific integrated circuits,programmable logic arrays and other hardware devices, can be constructedto implement one or more of the methods described herein. Applicationsthat may include the apparatus and systems of various embodiments oraspects can broadly include a variety of electronic and computingsystems. One or more embodiments or aspects described herein mayimplement functions using two or more specific interconnected hardwaremodules or devices with related control and data signals that can becommunicated between and through the modules, or as portions of anapplication-specific integrated circuit. Accordingly, the present systemencompasses software, firmware, and hardware implementations.

In accordance with various embodiments or aspects, the methods describedherein may be implemented by software programs tangibly embodied in aprocessor-readable medium and may be executed by a processor. Further,in an exemplary, non-limited embodiment or aspect, implementations caninclude distributed processing, component/object distributed processing,and parallel processing. Alternatively, virtual computing systemprocessing can be constructed to implement one or more of the methods orfunctionality as described herein.

It is also contemplated that a computer-readable medium includesinstructions 1220 or receives and executes instructions 1220 responsiveto a propagated signal, so that a device connected to a network 1224 cancommunicate voice, video or data over the network 1224. Further, theinstructions 1220 may be transmitted or received over the network 1224via the network interface device 1208.

While the computer-readable medium is shown to be a single medium, theterm “computer-readable medium” includes a single medium or multiplemedia, such as a centralized or distributed database, and/or associatedcaches and servers that store one or more sets of instructions. The term“computer-readable medium” shall also include any tangible medium thatis capable of storing or encoding a set of instructions for execution bya processor or that cause a computing system to perform any one or moreof the methods or operations disclosed herein.

In a particular non-limiting, example embodiment or aspect, thecomputer-readable medium can include a solid-state memory, such as amemory card or other package, which houses one or more non-volatileread-only memories. Further, the computer-readable medium can be arandom access memory or other volatile re-writable memory. Additionally,the computer-readable medium can include a magneto-optical or opticalmedium, such as a disk or tapes or other storage device to capture andstore carrier wave signals, such as a signal communicated over atransmission medium. A digital file attachment to an e-mail or otherself-contained information archive or set of archives may be considereda distribution medium that is equivalent to a tangible storage medium.Accordingly, any one or more of a computer-readable medium or adistribution medium and other equivalents and successor media, in whichdata or instructions may be stored, are included herein.

In accordance with various embodiments or aspects, the methods describedherein may be implemented as one or more software programs running on acomputer processor. Dedicated hardware implementations including, butnot limited to, application specific integrated circuits, programmablelogic arrays, and other hardware devices can likewise be constructed toimplement the methods described herein. Furthermore, alternativesoftware implementations including, but not limited to, distributedprocessing or component/object distributed processing, parallelprocessing, or virtual machine processing can also be constructed toimplement the methods described herein.

It should also be noted that software that implements the disclosedmethods may optionally be stored on a tangible storage medium, such as:a magnetic medium, such as a disk or tape; a magneto-optical or opticalmedium, such as a disk; or a solid state medium, such as a memory cardor other package that houses one or more read-only (non-volatile)memories, random access memories, or other re-writable (volatile)memories. The software may also utilize a signal containing computerinstructions. A digital file attachment to e-mail or otherself-contained information archive or set of archives is considered adistribution medium equivalent to a tangible storage medium.Accordingly, a tangible storage medium or distribution medium as listedherein, and other equivalents and successor media, in which the softwareimplementations herein may be stored, are included herein.

Thus, a system and method to define a rotational source associated witha biological rhythm disorder, such a heart rhythm disorder, has beendescribed herein. Although specific example embodiments or aspects havebeen described, it will be evident that various modifications andchanges may be made to these embodiments or aspects without departingfrom the broader scope of the invention. Accordingly, the specificationand drawings are to be regarded in an illustrative rather than arestrictive sense. The accompanying drawings that form a part hereof,show by way of illustration, and not of limitation, specific embodimentsor aspects in which the subject matter may be practiced. The embodimentsor aspects illustrated are described in sufficient detail to enablethose skilled in the art to practice the teachings disclosed herein.Other embodiments or aspects may be utilized and derived therefrom, suchthat structural and logical substitutions and changes may be madewithout departing from the scope of this disclosure. This DetailedDescription, therefore, is not to be taken in a limiting sense, and thescope of various embodiments or aspects is defined only by the appendedclaims, along with the full range of equivalents to which such claimsare entitled.

Such embodiments or aspects of the inventive subject matter may bereferred to herein, individually and/or collectively, by the term“invention” merely for convenience and without intending to voluntarilylimit the scope of this application to any single invention or inventiveconcept if more than one is in fact disclosed. Thus, although specificembodiments or aspects have been illustrated and described herein, itshould be appreciated that any arrangement calculated to achieve thesame purpose may be substituted for the specific embodiments or aspectsshown. This disclosure is intended to cover any and all adaptations orvariations of various embodiments or aspects. Combinations of the aboveembodiments or aspects, and other embodiments or aspects notspecifically described herein, will be apparent to those of skill in theart upon reviewing the above description.

The Abstract is provided to comply with 37 C.F.R. § 1.72(b) and willallow the reader to quickly ascertain the nature and gist of thetechnical disclosure. It is submitted with the understanding that itwill not be used to interpret or limit the scope or meaning of theclaims.

In the foregoing description of the embodiments or aspects, variousfeatures are grouped together in a single embodiment for the purpose ofstreamlining the disclosure. This method of disclosure is not to beinterpreted as reflecting that the claimed embodiments or aspects havemore features than are expressly recited in each claim. Rather, as thefollowing claims reflect, inventive subject matter lies in less than allfeatures of a single disclosed embodiment or aspect. Thus the followingclaims are hereby incorporated into the Detailed Description, with eachclaim standing on its own as a separate example embodiment or aspect. Itis contemplated that various embodiments or aspects described herein canbe combined or grouped in different combinations that are not expresslynoted in the Detailed Description. Moreover, it is further contemplatedthat claims covering such different combinations can similarly stand ontheir own as separate example embodiments or aspects, which can beincorporated into the Detailed Description.

The invention claimed is:
 1. A method of defining a rotational sourceassociated with a heart rhythm disorder, the method comprising:accessing, by a computing device, reconstructed signal data of heartsignals, the reconstructed signal data having activation onset timesassociated with voltages at a plurality of time points; transforming, bythe computing device, the reconstructed signal data from spline-sensorreferences to x-y coordinate locations; calculating, by the computingdevice, a plurality of center locations of wave fronts using thereconstructed signal data as transformed, at the plurality of timepoints associated with the rotational source, the wave fronts associatedwith the heart signals; determining, by the computing device, arotational path that connects the plurality of center locations; andgenerating, by the computing device, a clinical representation thatidentifies a region of heart tissue associated with the rotational path.2. The method of claim 1, wherein the method further comprisesdetermining each of the wave fronts to include adjacent locations havingat least a threshold voltage level surrounded by locations below thethreshold voltage level.
 3. The method of claim 2, wherein the thresholdvoltage level is a predetermined percentage of a highest voltage.
 4. Themethod of claim 1, wherein the method further comprises determining alikely core associated with the rotational path.
 5. The method of claim4, wherein determination of the likely core associated with therotational path comprises: calculating a plurality of relative diffusionshapes associated with the plurality of the center locations;determining a plurality of intersecting points of a smallest relativediffusion shape and other relative diffusion shapes within therotational path; and defining a bounded polygon of the intersectingpoints as the likely core.
 6. The method of claim 5, wherein calculationof a relative diffusion shape comprises: determining distances fromlocations in the wave front to a center location of the wave front; andcalculating a circle having a radius equal to a predetermined multipliermultiplied by a standard deviation of the distances.
 7. The method ofclaim 4, wherein determination of the likely core associated with therotational path comprises: determining a convex hull around therotational path; calculating a plurality of relative diffusion shapesassociated with the plurality of the center locations; determining aplurality of intersecting points of a smallest relative diffusion shapeand other relative diffusion shapes inside the convex hull; and defininga bounded polygon of the intersecting points as the likely core.
 8. Themethod of claim 1, wherein calculation of a center location of a wavefront comprises: averaging all first coordinates of locations associatedwith the wave front to generate a first average coordinate; averagingall second coordinates of the locations associated with the wave frontto generate a second average coordinate; and defining the centerlocation of the wave front as a location identified by the first averagecoordinate and the second average coordinate.
 9. A system to define arotational source associated with a heart rhythm disorder, the systemcomprising: a computing device; and a machine-readable medium to storeinstructions that, when executed by the computing device, cause thecomputing device to perform operations comprising: accessingreconstructed signal data of heart signals, the reconstructed signaldata having activation onset times associated with voltages at aplurality of time points; transforming the reconstructed signal datafrom spline-sensor references to x-y coordinate locations; calculating aplurality of center locations of wave fronts using the reconstructedsignal data as transformed, at the plurality of time points associatedwith the rotational source, the wave fronts associated with the heartsignals; determining a rotational path that connects the plurality ofcenter locations; and generating a clinical representation thatidentifies a region of heart tissue associated with the rotational path.10. The system of claim 9, wherein the operations further comprisedetermining each of the wave fronts to include adjacent locations havingat least a threshold voltage level surrounded by locations below thethreshold voltage level.
 11. The system of claim 10, wherein thethreshold voltage level is a predetermined percentage of a highestvoltage.
 12. The system of claim 9, wherein the operations furthercomprise determining a likely core associated with the rotational path.13. The system of claim 12, wherein operations for determination of thelikely core associated with the rotational path further comprise:calculating a plurality of relative diffusion shapes associated with theplurality of the center locations; determining a plurality ofintersecting points of a smallest relative diffusion shape and otherrelative diffusion shapes within the rotational path; and defining abounded polygon of the intersecting points as the likely core.
 14. Thesystem of claim 13, wherein operations for calculation of a relativediffusion shape further comprise: determining distances from locationsin the wave front to a center location of the wave front; andcalculating a circle having a radius equal to a predetermined multipliermultiplied by a standard deviation of the distances.
 15. The system ofclaim 12, wherein operations for determination of the likely coreassociated with the rotational path further comprise: determining aconvex hull around the rotational path; calculating a plurality ofrelative diffusion shapes associated with the plurality of the centerlocations; determining a plurality of intersecting points of a smallestrelative diffusion shape and other relative diffusion shapes inside theconvex hull; and defining a bounded polygon of the intersecting pointsas the likely core.
 16. The system of claim 9, wherein operations forcalculation of a center location of a wave front further comprise:averaging all first coordinates of locations associated with the wavefront to generate a first average coordinate; averaging all secondcoordinates of the locations associated with the wave front to generatea second average coordinate; and defining the center location of thewave front as a location identified by the first average coordinate andthe second average coordinate.
 17. A tangible computer-readable mediumstoring instructions that, when executed by a processor, cause theprocessor to perform operations for defining a rotational sourceassociated with a heart rhythm disorder, the operations comprising:accessing reconstructed signal data of heart signals, the reconstructedsignal data having activation onset times associated with voltages at aplurality of time points; transforming the reconstructed signal datafrom spline-sensor references to x-y coordinate locations; calculating aplurality of center locations of wave fronts using the reconstructedsignal data as transformed, at the plurality of time points associatedwith the rotational source, the wave fronts associated with the heartsignals; determining a rotational path that connects the plurality ofcenter locations; and generating a clinical representation thatidentifies a region of heart tissue associated with the rotational path.18. The tangible computer-readable medium of claim 17, wherein theoperations further comprise determining each of the wave fronts toinclude adjacent locations having at least a threshold voltage levelsurrounded by locations below the threshold voltage level.
 19. Thetangible computer-readable medium of claim 18, wherein the thresholdvoltage level is a predetermined percentage of a highest voltage. 20.The tangible computer-readable medium of claim 17, wherein theoperations further comprise determining a likely core associated withthe rotational path.
 21. The tangible computer-readable medium of claim20, wherein operations for determination of the likely core associatedwith the rotational path further comprise: calculating a plurality ofrelative diffusion shapes associated with the plurality of the centerlocations; determining a plurality of intersecting points of a smallestrelative diffusion shape and other relative diffusion shapes within therotational path; and defining a bounded polygon of the intersectingpoints as the likely core.
 22. The tangible computer-readable medium ofclaim 21, wherein operations for calculation of a relative diffusionshape further comprise: determining distances from locations in the wavefront to a center location of the wave front; and calculating a circlehaving a radius equal to a predetermined multiplier multiplied by astandard deviation of the distances.
 23. The tangible computer-readablemedium of claim 20, wherein operations for determination of the likelycore associated with the rotational path further comprise: determining aconvex hull around the rotational path; calculating a plurality ofrelative diffusion shapes associated with the plurality of the centerlocations; determining a plurality of intersecting points of a smallestrelative diffusion shape and other relative diffusion shapes inside theconvex hull; and defining a bounded polygon of the intersecting pointsas the likely core.
 24. The tangible computer-readable medium of claim17, wherein operations for calculation of a center location of a wavefront further comprise: averaging all first coordinates of locationsassociated with the wave front to generate a first average coordinate;averaging all second coordinates of the locations associated with thewave front to generate a second average coordinate; and defining thecenter location of the wave front as a location identified by the firstaverage coordinate and the second average coordinate.